...
Lv 4
... asked in 科學及數學化學 · 10 years ago

chem mc (已知答案,求解)

An iron nail is heated with concentrated sulphuric acid. which folling combinations is correct??

Gas given off Colour of solution formed

A.hydrogen pale green

B.htdrogen yellow

C.sulphur dioxide pale green

D. sulphur dioxide yellow

ANS:D

請問why is D and why isnot A B C

1 Answer

Rating
  • 10 years ago
    Favorite Answer

    The answer is: D. sulphur dioxide.... yellow

    Iron reacts with common acid to give iron(II) and hydrogen.

    Fe(s) + 2H^+(aq) → Fe^2+(aq) + H2(g)

    Hydrogen is given off and the solution becomes pale green due to the presence of iron(II) ions.

    However, concentrated sulphuric acid, on heating, is a rather strong oxidizing agent. The above reaction thus does not occur. Instead, a redox reaction occurs.

    2Fe(s) + 6H2SO4(conc) → Fe2(SO4)3­(aq) + 6H2O(l) + 3SO2(g)

    Refer to the above equation. Sulphur dioxide gas is given off, and the solution becomes yellow due to the presence of iron(III) ions.

    Therefore, the key is D. A, B and C are incorrect.

    Source(s): sioieng
Still have questions? Get your answers by asking now.